Abstract The NIA Interventions Testing Program represents a multi-site translational research program to evaluate agents hypothesized to extend mouse lifespan by retardation of aging or postponement of late life diseases. Interventions proposed by multiple collaborating scientists from the research community are initially tested, in parallel, at three sites (Jackson Laboratories, Michigan and Texas), using identical, standardized protocols, and using sufficient numbers of genetically heterogeneous mice to provide 80% power for detecting changes in lifespan of 10%, for either sex, after pooling data from any two of the test sites. Forty such lifespan experiments, involving various doses of 25 distinct agents, have been initiated in the first nine years of the ITP. Significant effects on longevity, in one or both sexes, have been documented for 5 of the tested agents: aspirin, NDGA, rapamycin, Acarbose, and 17--estradiol. Initial lifespan trials are now underway for 8 agents, as well as comprehensive analyses of the effects of rapamycin, Acarbose, and NDGA on health and on cellular and physiological traits thought likely to mediate the beneficial effects seen. Plans for the next five year period include additional lifespan (Stage I) trials, detailed analyses (Stage II) of agents found to increase lifespan, and some increased emphasis on collaborations with other scientists skilled at evaluating traits related to health and disease or at testing ideas about mechanisms of drug action on aging. Each of the three ITP laboratories will bring special expertise to the effort: measures of age-sensitive traits at the Jackson Laboratory, pathology and statistical analysis at Michigan, and pharmacology at the University of Texas.